(a) Name the device used for producing an electric current from a chemical (b) Copy and complete the table below. Electrolyte Product at the anode (carbon) ...

Answer Details

(a) The device used for producing an electric current from a chemical reaction is an electrochemical cell (also called a galvanic or voltaic cell, or simply a chemical cell).

(b) Completed table

Reasoning:

• In dilute \( NaCl_{(aq)} \) the solution is mostly water. At the anode, \( OH^- \) is discharged in preference to the dilute \( Cl^- \), giving oxygen. At the cathode, \( H^+ \) is discharged in preference to \( Na^+ \) (sodium is high in the electrochemical series), giving hydrogen.
• In concentrated \( NaCl_{(aq)} \) the high concentration of \( Cl^- \) causes chloride to be discharged at the anode instead of \( OH^- \), giving chlorine. Hydrogen is still liberated at the cathode.

Electrode half-equations: at the cathode \( 2H^+ + 2e^- \rightarrow H_2 \); at the dilute anode \( 4OH^- \rightarrow O_2 + 2H_2O + 4e^- \); at the concentrated anode \( 2Cl^- \rightarrow Cl_2 + 2e^- \).